1. Field of the Invention
The invention relates to a hybrid vehicle running control apparatus. More particularly, the invention relates to a running control apparatus that is mounted in a hybrid vehicle that has a high-voltage battery and a low-voltage battery, and is selectively controlled to drive in a first running mode in which an electric motor to which power is supplied from the high-voltage battery is used as a drive source, and a second running mode in which an engine is used as the drive source.
2. Description of Related Art
Japanese Patent Application Publication No. 2006-174619 (JP 2006-174619 A), for example, describes a related running control apparatus of a hybrid vehicle that has a high-voltage battery, a low-voltage battery, and a DC-DC converter that performs voltage conversion between the high-voltage battery and the low-voltage battery, and is selectively controlled to drive in a first running mode (an EV running mode) in which an electric motor to which power is supplied from the high-voltage battery is used as a drive source, and a second running mode in which an engine is used as the drive source.
This running control apparatus activates a controller at regular intervals of time, after an ignition switch has been switched from on to off. Every time the controller is activated, power is supplied from a high-voltage main battery to a low-voltage auxiliary battery via a DC-DC converter to charge the auxiliary battery. Therefore, even if the hybrid vehicle is left for an extended period of time, the auxiliary battery will be charged at regular intervals of time using the main battery. As a result, the auxiliary battery is able to be prevented from going dead.
The technology described in JP 2006-174619 A is implemented when there is at least a predetermined capacity remaining (i.e., SOC: state-of charge) in the main battery. On the other hand, the main battery is typically charged to full charge when a vehicle is assembled. In a hybrid vehicle, EV running is allowed when the SOC (state-of-charge) of the main battery is equal to or greater than a predetermined SOC, and EV running is prohibited when the SOC is below the predetermined SOC. Therefore, if EV running is allowed when vehicle transport from when the hybrid vehicle is assembled until the vehicle is delivered takes a long period of time, such as when a hybrid vehicle is an export, the SOC of the main battery tends to decrease with this transport. As a result, the life of the main battery may decrease, and charging the auxiliary battery may be difficult.